/Engine/Source/Editor/UnrealEd/Public/EditorViewportClient.h
Returns true if preview actors were updated
virtual bool UpdateDropPreviewActors ( int32 MouseX, int32 MouseY, const [TArray](API\Runtime\Core\Containers\TArray)< [UObject](API\Runtime\CoreUObject\UObject\UObject) * > & DroppedObjects, bool & out_bDroppedObjectsVisible, [UActorFactory](API\Editor\UnrealEd\ActorFactories\UActorFactory) * FactoryToUse )